of cardonald



D. COCKBURN AND D. MAcNICOLL.

SAFETY VALVE.

APPLICATION FILED FEB. s. 1919.

1 ,322, 179. Patented Nov. 18, 1919.

UNITED STATES PATENT OFFICE,

DAVID GOCKBURN AND DONALD MACNICOLL, 0F CAR-DONALD, NEAR GLASGOW, SCOTLAND, ASSIGNORS TO GOCKBURNS, LIMITED, OF CARDONALD, NEAR GLASGOW, SCOTLAND.

SAFETY-VALVE.

Specification of Letters Patent.

Patented Nov. 18, 1919.

To all whom it may concern:

Be it known that we, DAVID CooKBimN and DONALD MAcNIcoLL, both subjects of the King of the United Kingdom of Great Britain and Ireland, and residing at Cardonald, near Glasgow, Scotland, have invented a certain new and useful Improvement in Safety-Valves, of which the following is a specification.

This invention relates to improvements in safety valves of the type fitted with a piston member positioned above the valve proper and movable to effect increased lift of the valve proper.

The figure of the accompanying drawing is a part side elevation part vertical section of a safety valve according to the in vention.

As shown, fitted to surround loosely the valve spindle 1 is a piston member 2 of greater area than the cross-sectional area of the opening at the valve seat 3.

Normally the piston 2 rests on the upper end of the body of the valve proper 4 so that on upward movement of the valve proper the piston 2 will be positively lifted.

On the valve spindle 1 above the piston is a collar 5.

6 denotes a cylindrical wall forming the lateral boundary of a cylindrical chamber above the valve seat 3, which chamber, when the valve proper is in engagement with the valve seat, is in communication with the waste steam space above the valve proper, being so spaced from the valve seat as to be then unoccupied by the piston, but which is cut off from such waste steam space by the piston 2 when said piston rises with the valve proper; the piston being a fit within the cylindrical chamber.

In operation, when the valve proper rises from its seat, the piston 2 also rises as aforesaid and entering the cylindrical chamber is forced upwardly against the collar 5 by the pressure of steam on the under side of the piston 2, whereby there may be obtained increased lift of the valve proper.

It will be seen that any tendency the piston 2 may have to bind in the cylindrical chamber will not prevent the valve proper from rising.

It will be understood that it is important that the cylinder should normally be unoccupied by the piston. In the construction according to the prior Patent No. 1262641 in which the piston is continuously in occupation of the cylinder, a pool of condensate water is apt to collect, in the cylinder above the piston, so that the piston is liable to become jammed. The present construct-ion obviates the formation of such a pool.

What we claim is In a safety valve, in combination, a valve seat member having an opening, a valve proper to control said opening, a valve spindle, having a collar above said valve proper, a piston slidable on said spindle independently of said valve, said piston being below said collar and adapted to be lifted when said valve proper rises out of engagement with said seat member, said piston being of greater area than said opening, and a cylinder above said seat member, said cylinder being so spaced from said seatmember as to be unoccupied by said piston when said valve proper is in engagement with said seat member, said cylinder adapted to receive said piston on the rise of said valve proper.

In testimony whereof we have signed our names to this specification in the presence of two subscribing witnesses.

DAVID COCKBURN. DONALD MAGNIOOLL.

ANNE R. WVATT. 

